1. Field of the Invention
The present invention relates to a steering device including a tilt/telescopic mechanism, the steering device being capable of suppressing variation in a tightening force that occurs in a tightening state due to a level of a height position of an outer column by tilt adjustment and also capable of maintaining stable tightening rigidity.
2. Description of the Related Art
One type of the steering device including the tilt/telescopic mechanism is a steering device including an outer column that supports a steering shaft to be able to slide in an axial direction and to be fixed. The outer column moves up and down with respect to a fixed bracket. As the steering device of this type, there is a steering device disclosed in Japanese Patent Application Laid-Open No. 2007-223383 (Patent Literature 1). Details of the steering device disclosed in Patent Literature 1 are generally explained below, with components denoted by reference numerals and signs in parentheses.
Contact surfaces (16A, 16B) are formed in the vicinity of the axis of an outer column (1) on left and right side surfaces of the outer column (1). When a tightening rod (34) is loosened, the contact surfaces (16A, 16B) have slight gaps between the contact surfaces (16A, 16B) and inner side surfaces (321A, 321B) of side plates (32A, 32B). When the tightening rod (34) is tightened, the contact surfaces (16A, 16B) respectively come into contact with the inner side surfaces (321A, 321B) of the side plates (32A, 32B).
As shown in FIG. 3 of Patent Literature 1, the contact surfaces (16A, 16B) extend to a vehicle body rear side from a vehicle body front side end face (14) of the outer column (1) and are formed to a position slightly beyond vehicle body rear ends of telescopic long grooves (12A, 12B) formed in clamps (11A, 11B). Therefore, the contact surfaces (16A, 16B) come into contact with inner side surfaces (321A, 321B) of the side plates (32A, 32B) over the entire length of a telescopic position adjustment range of the outer column (1).
On side surfaces of the clamps (11A, 11B), contact surfaces (17A, 17B) are formed in the vicinity of the axis of the tightening rod (34). The contact surfaces (17A, 17B) are lightly in contact with the inner side surfaces (321A, 321B) of the side plates (32A, 32B) even when the tightening rod (34) is loosened. The contact surfaces (17A, 17B) are capable of coming into contact with the inner side surfaces (321A, 321B) of the side plates (32A, 32B) over the entire length of the telescopic position adjustment range of the outer column (1).
In Patent Literature 1, the contact surfaces (16A, 16B) extend to the vehicle body rear side from the vehicle body front side end face (14) of the outer column (1). The contact surfaces (17A, 17B) are formed to extend long in the axial direction over the entire length of the telescopic position adjustment range of the outer column (1). Therefore, the contact surfaces (16A, 16B) and the contact surfaces (17A, 17B) are formed to be in long surface contact, in the axial direction, with the inner side surfaces (321A, 321B) of the side plates (32A, 32B) of a vehicle body attachment bracket (3).
However, the vehicle body attachment bracket (3) is a metal plate. The side plates (32A, 32B) bend when the tightening rod (34) is tightened. The contact surfaces (16A, 16B) and the contact surfaces (17A, 17B) do not entirely come into contact with the side plates (32A, 32B) but partially come into contact with the side plates (32A, 32B).
Bending sections differ from vehicle to vehicle and tightening operation to tightening operation. It is likely that sections requiring contact most, that is, sections having weak rigidity, are not in contact with the contact surfaces (16A, 16B) and the contact surfaces (17A, 17B). Then, it is likely that a difference in rigidity in the axial direction of the outer column (1) increases and tightening rigidity decreases. The contact surfaces (16A, 16B) and the contact surfaces (17A, 17B) are formed long in the axial direction. Machining is also applied to sections that the contact surfaces (16A, 16B) and the contact surfaces (17A, 17B) do not come into contact with because of the bending of the side plates (32A, 32B). Therefore, there are many machined surfaces, costs increase, and weight also increases.